This DIY is pretty good:
Pelican Technical Article: Boxster Radiator Replacement and Cleaning - 986 / 987
Two hints from when I did this a few years ago: Be very careful not to damage the AC condenser or refrigerant lines in the process. Others have cracked the condenser and their project mushroomed exponentially. Also follow the Pedro coolant replacement DIY and carefully purge the air out of all the tight coolant passages in your motor. Failure to get all the air out risks a serious motor overheat and possible cracked heads. The process of changing the radiator is pretty simple. The cost of not doing it carefully is high.